I have been trying to upgrade my local hosted VM ERPNext. Did a git pull from bench-repo and then bench update --upgrade from frappe-bench. I have exported the VM and reimported on another server for this update trial. This is the error I have been getting a couple of times. Any idea of what needs to be done to complete the upgrade? Thanks. 
No. First time update. I have tried with another VM copy and had the same problem. So I imported a clean copy, did a git pull and installed nodejs 6.x and did a new bench update.